The maintenance of clear vision during head movements relies on a significant contribution from signals arising int he vestibular labyrinth that are used to provide information on head acceleration and head orientation with respect to the gravity vector and to generate outputs that help to produce compensatory eye and head movements that stabilize images on the retina. In previous work on this project, we have produced new information on the responses of neurons in the vestibular nuclei that represent spatial and temporal transformation of the sensory signal into appropriate driving signals for vestibulo-ocular responses to either static head tilt or translational head movement. Those data were obtained in decerebrated preparations. We now propose to extend those studies to alert primates that are trained to track or fixate visual targets with eye movements. In addition, we will evaluate linear acceleration related responses for vectors of acceleration that are applied in both vertical and horizontal head planes. Our anatomical studies of otolith organ-related afferents have identified projections into the midline cerebellar cortex. These and other central projections of the separate branches of the vestibular nerve will be reexamined in anatomical studies performed on primates to determine whether the sensory projections differ from gerbils in relationship to species dependent differences in vestibulo-ocular functions. An extension and continuation of morphological studies of primary afferents is proposed. otolith organ-related afferents will be functionally characterized by their responses to pure linear acceleration. A model based on those three-dimensional reconstruction of individual intracellularly labeled afferents will be developed to relate the distribution of different classes of the projections of otolith afferents to central nuclei that contain postsynaptic neurons with different response properties.